Bifocal lens



A 8 1933- H. A. TOULMIN, JR 1,924,336

BIFO-CAL LENS ori inal Filed Jil 6, 1931- 2 Sheets-Sheet 1- WWQQW 4 i 6 I a INVENTOR HARRY A. TOULM/N JR.

ATTORNEY Aug.- 29,.1933. H. A. TOULMIN, JR 7 5 B1FocAL LENS ori inal Filed July 6, 1931 2 Sheets-Sheet 2 .gyzz. 13.

INVENTOR HARRY A. TOUZMJN J ATTQRNEY Patented Aug 29, 1933 UNITED STATES PATENT OFFICE Original application July 6, 1931, Serial No.

Divided and this application March 21,1932. Serial No. 600,232

9 Claims. (01. 49--82.1)

My invention relates to bifocal eyeglass lenses and the method of manufacturing.

It is the object of my invention to provide a very cheap and accurate method of manufacturing a bifocal eyeglass lens and of providing a resulting lens that requires the minimum of skill in its production, as well as materials of of the cut-through type, thatis, the type with the insert extending completely through the major lens, which can be cheaply and efficiently manufactured and eliminates the difliculties which heretofore have existed in manufacturing a lens in which the major lens had to be pierced in order to insert the near vision portion, with the consequent difficulties of fusing, particularly the near vision insert within the distance portion of the lens, when using glasses of different melting points and of different indices of refraction.

This application is a division of my copending application, Serial No. 548,757, filed July 6, 1931.

Referring to the drawings, Figure 1 is a perspective of the assembled, unfused raw stock blank. 1

Figure 2 is a similar view after fusing.

Figure 3 is a plan view after the fused raw j stock blank has been cut to marginal form and ground to shape.

Figure 4 is a section on the line 4--4 of Figure 3.

Figure 5 is a view similar to Figure 2 except that it shows the arrangement of a blank for making a cut-through type of lens.

Figure 6 is a section through such a lens as finally manufactured, such section being taken on the line similar to that of Figure 4.

Figure '7 is a perspective of the insert for the near vision portion, such as of flint or bariu crown glass showing the greyed edge.

' Figure 8 is a section through the finished bifocal eyeglass lens, the blank for which is shown in Figure. 4. g

Figure 9 is a perspective of a blank having alternate inserts of flint and crown glass. I

Figure 10 is a plan view of the lens resulting from the blank shown in Figure 9.

Figure 11 is a perspective of a blank in which an arcuate back insert that can be rocked to its desired position may be employed.

of the blank in Figure 12.

Referring to the drawings in detail, I assemble rectangular strips or blocks of crown glass 1, 2 and 3 to form a major blank. I provide a minor portion by laying between the surface 4 of the block 1 and the surface 5 of the block 2 a bar or strip 6 of fiint glass or of barium crown glass. The upper and lower surfaces 7 and 8 of this bar of glass 6 are preferably roughened to form a grey edge. This roughening may be imparted by chemical action, by mechanical action, or by sand blasting. Its purpose is to prevent the reflection of light in the resulting lens. I also may, but it is not essential, roughen the, adjacent faces 4 and 5 of the crown glass members 1 and 2 where they engage the grey surfaces 7 and 8 of the bar 6.

I place the bar 3 in-engagement at the back of the fiint bar 6 and between the surfaces 4 and 5 of the crown glass blocks 1 and 2.

The composite structure is then fused with the result shown in Figure 2 so that the back 9 and the top edges '7 and 8 of the bar 6 are fused to the blocks 1, 2 and 3. The rough bifocal blank thus r fused is then trimmed as in Figure 3 to the desired outline and the trimmed block is ground to form a semi-finished bifocal blank as shown in Figure 4. To produce the finished lens shown in Figure 8, the-non-segment surface of the semifinished bifocal blank is surfaced with a curvature suitable for the particular prescription.

In Figures 5 and 6 are shown the raw stock bar and the section of the finished blank where -a cut-through lens is desired. Heretofore, to

make a cut-through lens, it has been the practice to take the major lens of the distance portion of the crown glass, bore a' hole through the glass and then plug the hole with a piece of flint glass. Then the lens blank was fused. The diflicultie: of making such a lens have been numerous, amongst them being the difficulty of grinding the hole accurately, the difliculty of grinding the .margin of the insert to fit the hole, and the difliculty of fusing due to the difference in diameter of the segment and the diameter of the hole necessary for the insertion of the insert in the, hole.

1 Furthermore, the adjacent edges of the insert andthe hole could not be roughened to furnish a grey surface to prevent light reflection because no this roughening would upset the accuracy of the fit.

By the present arrangement, relatively unskilled labor can be employed andmaximum production secured by welding the three bars together having adjacent grey faces and then flnishing the bars in their welded condition to the A proper marginal and angular configuration for an eyeglass lens as shown in Figure 6. The lens can then be ground into its finished form. according to the prescription of the wearer. Ordinarily straight bar flat surfaces are employed and no difflculties are encountered in quantity manufacture.

The resulting lens has structural advantages for the wearer that are important. In the flrst place, by varying the depth of the bar 6, any depth of reading segment may be employed. As the bar 6 runs completely across the lens, the maximum width of reading field is secured. If desired, the bar 2 may beof suflicient depth to permit of seeing at a distance beneath the bar 6. By adequate grinding, the optical center of the insert can be adjusted to the needs of the wearer.

Referring to Figure 9, it will be observed that if it is desired to see at a distance on either side of the block 6, that by using the crown insert blocks 10 this result may be secured. The result ing lens is shown in Figure 10. The advantage of arcuate face crown block 13, having a corresponding arcuate face 14 receiving the face 12 of the insert 11, it is possible to rock the insert 11 in any angular position and fuse it in that position with the result shown in Figures 12 and 13. As

. shown in Figure 13 the optical center has been placed in the smaller part of the insert, as distinguished from the upper part of the insert.

Thus by this system of building a lens, with strips-or bars of glass having plane flat surfaces or simple cylindrical surfaces, quantity production of very accurate lenses can be secured and raw stock from which lenses are made can be produced with continuous production methods, thus materially reducing the cost without sacrificing accuracy and with an improvement in the reading qualities of the lenses.

It will be understood that I desire to comprehend within my invention the 7 use of any type of glass and that when I use the term crown glass" or ,flint glass I do not intend to be confined to this particular type ofglass. Furthermore, it will be understood that instead of building up the a rough blank as in Figures 1 and 2, I may select a plate of crown glass and mill a rectangular slot in the face thereof for the reception' of the flint glass insert, although I prefer a built up method as a quicker and cheaper method, requiring no expert grinding. Likewise a transve se cut-away depression may be formed in the face of the crown glass plate, having an arcuate bottom for the reception 'o'fthe rocking flint insert shown. in Figures 11, 12 and 13.

Having thus fully described my invention, what I claim' as new and desire to secure by Letters Patent, is:

1. In a method of producing bifocal lenses, forming a major blank by assembling a plurality of rectangular crown glass strips, arranging a flint glass strip so that it is engaged on at least its top and bottom walls by the crown glass. and fusing said strips together by a single fusion.

2. In a method of producing bifocal lenses, forming a major blank by assembling strips of crown glass, arranging a strip of flint. glass so that the top, back and bottom walls of the flint glass are surrounded and engaged by the. crown' of said glass strips, joining such abutting faces and fusing the strips one to the other by a single fusion.

- 4. In a method of producing bifocal lenses, forming a major blank by assembling a plurality of strips of crown glass to form a channel in one face of the assembled strips,'inserting a strip of flint glass therein, and providing the upper and lower engaging faces between the flint and crown glass with a grey surface.

5. In a method of producing lenses, providing a major blank of crown glass with a ridged depression in the face thereof extending completely across the face, inserting a strip of flint glass therein and fusing.

6.In a method of producing a bifocal lens having a one-piece insert, providing a plate of glass of one index of refraction with a slot arranged transversely of the face thereof, inserting a bar of glass of a different index of refraction in said slot, and fusing the two pieces of glass to one another.

7. In a method of producing a bifocal lens having a one-piece insert, cutting a slot of rectangular cross section in the face of a plate of glass of one index of refraction for distance vision, inserting a one-piece rectangular insert of a different index of refraction, and completing the lens blank in a single fusing operation by fusing the two pieces of glass to one another.

8. In a method of manufacturing a bifocal lens forming a rigid recess in the face of'a major blank, placing a one-piece insert of glass of a different index of refraction in said recess, and

of refraction, inserting between said blocks in said slot a piece of glass comprising a one-piece insert of a difierent'index ofrefraction, and completing the lens by a single fusing of all of said blocks one to the other.

HARRY-AUBREY TOULMIN, JR. 

